Alert Sounds Stopped Working

I downloaded a .wav, cropped it using Audacity then saved it as a .aiff (Apple/SGI 16 bit PCM). I put it in the System sounds folder and now I can't get ANY of the alert sounds to work. I removed the offending file but still can't get any alert sounds to work. I've done this before on my G3 iMac running 10.2.8 without a prob. I'm now using a G5 iMac running 10.4.1.